TW202212781A - Flow rate measurement device - Google Patents

Abstract

Provided is a flow rate measurement device capable of reliably correcting a measurement error due to the temperature of a to-be-measured fluid. In the present invention, a vortex generator 32 is inserted to a flow path 31 in a measurement pipe 30 so as to generate a Karman vortex on the downstream side of the vortex generator 32, a temperature sensor 36 is disposed in a rear stage of a piezoelectric element 35 that detects a vortex change as an electric signal change, and a fluid flow rate is corrected on the basis of the relation between a vortex frequency at a fluid temperature measured with the temperature sensor 36 and a vortex frequency at a fluid reference temperature.

Description

Flow measurement device

The present invention relates to a flow measuring device.

Previously, it has been known that if an obstacle is placed in the flow of the fluid, mutually different regular vortices (Kaman vortices) will be generated downstream of the obstacles, and a device for measuring the flow rate using the Karman vortices has been proposed. The Karman vortex flow measuring device is excellent in pressure loss reduction, rapid response speed, and simple structure. The industry has proposed the use of mechanisms for detecting Karman eddy currents, piezoelectric elements, strain gauges, capacitive sensors, shuttle pistons, thermal resistors and ultrasonic detection methods.

The schematic structure of the main components of a general vortex flowmeter is shown in FIG. 1 . As shown in FIG. 1 , a general vortex flowmeter includes: a vortex generator 3 that generates a Karman vortex 2 in a flow 1 in a pipe, a detecting element 4 that detects the eddy current, and a device that processes the signal detected by the detecting element 4 converter. A Karman vortex is generated downstream of the vortex generator 3 placed in a right-angle direction with respect to the flow path. It is known that the generation frequency of the Karman vortex is proportional to the velocity (velocity) of the fluid, and the relational expression is as shown in the following formula (1). f=St(v/d) (1) Here, f is the vortex frequency (1/sec), v is the average flow velocity of the fluid (m/sec), d is the width of the vortex generator (m), and St is a constant called the Streux number.

On the other hand, if the cross-sectional area of the flow path is S (m ² ), the flow rate Q (m ³ /sec) can be obtained by the following formula (2). Q=v×S (2) From the formula (1), if v=(f×d)/St is substituted into the formula (2), the following formula (3) is obtained. Q=(f×d)×(S/St) (3)

Since the width d(m) of the eddy current generator and the cross-sectional area S(m ² ) of the flow path are constant, if the Streux number St is constant and k is constant, the flow rate Q(m ³ /sec) ) can be represented by the following formula (4). Q=f×k (4) Therefore, the flow rate Q can be obtained by detecting the eddy current frequency f.

In addition, the Stroke number changes according to the Reynolds number, and the Reynolds number Re is defined by the following formula (5). Re=(ρv2)/(μv/D) =v×D/ν (5) Here, ρ is the density of the fluid (kg/m ³ ), v is the average fluidity of the fluid (m/sec), and μ is the density of the fluid (kg/m 3 ) The viscosity coefficient of the fluid (kg/m•sec), D is the width of the flow path (m), and ν is the kinematic viscosity coefficient (m ² /sec).

According to the above formula (5), the Reynolds number is a function of the kinematic viscosity coefficient, and the kinematic viscosity coefficient changes according to the temperature of the fluid, so there may be errors in measuring the flow rate due to the actual temperature of the fluid. Therefore, in the method of measuring the flow rate using the Karman vortex, it is necessary to correct the measured flow rate.

For example, Patent Document 1 discloses a temperature sensor-integrated vortex flowmeter 11 as shown in FIG. 2 . It is described that the temperature sensor-integrated vortex flowmeter 11 includes a measuring tube 12, a vortex generator 13, and an eddy current detection sensor 15 having a built-in temperature sensor 14, and the vortex generator 13 forms a measurement with one end open. In the chamber 16, a pressure guiding hole 17 is formed in the measurement chamber 16 in a direction perpendicular to the flow of the fluid to be measured. The eddy current detection sensor 15 includes a vibration tube 18 and an eddy current detection unit 19. The vibration tube 18 includes an insertion measurement The movable tube part 20 of the chamber 16 and the pressure receiving plate 21 connected to one end of the movable tube part 20 flow the fluid to be measured in the flow path 22 of the measurement tube 12. If the Karman eddy current is generated, the eddy current detection part 19 will detect the fluid. The pressure fluctuation caused by the Karman eddy current received by the vibrating tube 18 is converted into an electrical signal and output to the mass converter. The temperature correction mechanism in the mass converter corrects the indicated temperature of the temperature sensor 14 and calculates the mass flow rate . [Prior Art Literature] [Patent Literature]

Patent Document 1: Specification of Japanese Patent No. 3964416

[Problems to be Solved by Invention]

In Patent Document 1, a temperature sensor-integrated vortex flowmeter is disclosed, but it simply includes a temperature correction mechanism, and the specific structure of the temperature correction mechanism is unknown, and it is difficult to correct the flow rate error due to the temperature of the fluid to be measured. .

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a flow rate measuring device that can reliably correct a flow rate error caused by the temperature of the fluid to be measured. [Technical means to solve problems]

In order to solve the above-mentioned problems, the flow measurement device of the present invention includes: a vortex generator inserted into the flow of the fluid; and a detection element that detects a change in the Karman eddy current generated on the downstream side of the vortex generator as a change in an electrical signal A circuit, which converts the above-mentioned electrical signal into an eddy current frequency; and an arithmetic circuit, which calculates the flow rate of the fluid based on the above-mentioned eddy current frequency; The flow measuring device is characterized in that a temperature sensor is arranged after the detection element, and the above-mentioned calculation is performed. The circuit is provided with the temperature t ₀ , t ₁ , t ₂ , ..., t _n (t ₀ <t ₁ < _{t 2} <... In the correction table of the relationship, if the temperature of the fluid measured by the above temperature sensor is set as t, the frequency of the eddy current converted from the electrical signal detected by the above detection element is set as f, when the above temperature t is related to the eddy current When the frequency f and the temperature in the above correction table are consistent with the eddy current frequency, the flow rate at the matched eddy current frequency is output as the corrected flow rate; when the above temperature t is equivalent to the temperature t ₀ , t in the above correction table ₁ , t ₂ , ・・・, or t _n , but when the above correction table does not have the above eddy current frequency f, there is a linear relationship between the amount of change in the estimated eddy current frequency and the amount of change in the flow rate, which will be calculated by the above calculation circuit. The flow rate at the output eddy current frequency f is output as the corrected flow rate; when the above temperature t does not conform to any of the temperatures in the above correction table, and the temperature t is included in the temperatures t ₀ , t ₁ , t ₂ , ·・・, or between any two temperatures t _α and t _β adjacent to t _n , there is a linear relationship between the amount of change in the estimated temperature and the amount of change in the eddy current frequency, and the temperature t is calculated by the above-mentioned operation circuit The eddy current frequency below, and the change of the estimated eddy current frequency and the change of the flow rate Q have a linear relationship, and the flow rate at the eddy current frequency f calculated by the above arithmetic circuit is output as the corrected flow rate.

Fig. 3 is a schematic structural diagram of an embodiment embodying the flow rate measuring device of the present invention. In FIG. 3, 31 is the flow path in the measuring tube 30, and the fluid flows in the direction of the arrow. The eddy current generator 32 is arranged in the flow path 31 . The Karman vortex is generated on the downstream side of the vortex generator 32 when the fluid flowing in the flow path 31 in the measurement tube 30 comes into contact with the vortex generator 32 .

33 is a Karman eddy current detector installed on the downstream side of the eddy current generator 32, and has a built-in piezoelectric element 35 (a detection element that detects changes in Karman eddy current as changes in electrical signals) and a cylindrical temperature sensor 36. The element holding parts 34, 37a, 37b are lead wires.

In the above configuration, when the element holding portion 34 vibrates due to the reaction of the Karman vortex generated on the downstream side of the vortex generator 32 by the fluid flowing in the measuring tube 30 contacting the vortex generator 32, the element holding portion 34 vibrates. The vibration is detected by the piezoelectric element 35 and converted into an electrical signal. If the temperature sensor is arranged on the upstream side of the eddy current generator 32 , an obstacle is arranged before the eddy current generator 32 , which may affect the generation of the eddy current. Therefore, the temperature sensor 36 is arranged downstream of the piezoelectric element 35 . side. To this end, the flow rate of the fluid can be corrected based on the amount of change in the vortex frequency due to the temperature of the fluid measured by the temperature sensor 36 .

However, in the fluid to be measured, there are also corrosive chemicals used as cleaning fluids for industrial equipment. If the measurement object is a corrosive chemical solution, the constituent material of the flow measurement device must be made of a material resistant to the corrosive chemical solution. For this reason, the temperature sensor 36 is preferably protected by a chemical-resistant material (a material that is resistant to corrosive chemicals). Furthermore, the material constituting the flow path 31 through which the fluid flows, the vortex generator 32 for generating the Karman vortex, and the piezoelectric element 35 are preferably protected by chemical-resistant materials. The chemical resistance material is preferably a fluororesin such as PFA (perfluoroalkoxyalkane) or PTFE (polytetrafluoroethylene), which is excellent in acid resistance, alkali resistance, and organic solvent resistance. In addition, the eddy current generator 32 which is an embodiment of this invention is made of PFA.

In order to suppress the change in the cross-sectional area of the flow path due to temperature change, the linear expansion coefficient of the material constituting the flow path is preferably small. The linear expansion coefficient of PFA or PTFE is 12.4×10 ^-5 /℃ at around 20～100℃, and the linear expansion coefficient of borosilicate glass with excellent acid and alkali resistance is 3.2×10 ^-6 at 0～350℃ /℃, which is more than one order of magnitude smaller than PFA or PTFE, so it is better as a material for the flow path; quartz has excellent acid resistance and alkali resistance, and the linear expansion coefficient at 0 ~ 100 ℃ is 0.52 × 10 ^{- 6} /°C is more than 2 orders of magnitude smaller than that of PFA or PTFE, so it is more suitable as a constituent material of the flow path.

In addition to the constituent material of the flow path, that is, if the temperature sensor 36 and the piezoelectric element 35 are protected by PFA or PTFE, measurement errors due to changes in cross-sectional area due to temperature rise will not occur. For this reason, when the measurement object is a corrosive chemical liquid, it is preferable to coat the temperature sensor 36 and the piezoelectric element 35 with PFA or PTFE. In addition, if fillers such as glass fiber or carbon graphite are mixed with PFA or PTFE at about 20 to 25% by weight, the coefficient of linear expansion can be reduced by about 20 to 40%, which is more preferable. In addition, the element holding part 34 and the measuring tube 30 of this embodiment are made of PFA. [Effect of invention]

The flow measuring device of the present invention can insert an obstacle in the flow of the fluid, generate a Karman eddy current on the downstream side, and arrange a temperature sensor after the detection element that detects the change of the eddy current as a change of the electrical signal. The amount of change in the eddy current frequency due to the temperature of the fluid measured by the above temperature sensor accurately corrects the flow rate of the fluid.

Hereinafter, based on embodiment, this invention is demonstrated in detail. In addition, the embodiment described below is exemplification, and the present invention is not limited to the embodiment, and various changes and corrections can be made without departing from the technical scope of the present invention.

The present invention is characterized in that a temperature sensor is disposed after a piezoelectric element that detects changes in Karman eddy currents as changes in electrical signals, and is based on changes in eddy current frequency due to the temperature of the fluid measured by the temperature sensor. However, the following describes the specific correction procedure.

That is, in the flow measurement device shown in FIG. 3 , the Karman vortex is generated on the downstream side of the vortex generator 32 by the fluid flowing in the flow path 31 in the measuring tube 30 abutting against the vortex generator 32 . The piezoelectric element 35 in the element holding portion 34 of the Karman eddy current detector 33 disposed on the downstream side of the eddy current generator 32 is converted into an electrical signal, and is transmitted to the electric signal through the wire 37a, which is surrounded by a dotted line in FIG. 4 . The electric charge voltage conversion circuit, differential circuit, filter circuit, eddy current frequency measurement circuit and CPU of the circuit part. On the other hand, the temperature data measured by the temperature sensor 36 at the rear stage of the piezoelectric element 35 disposed in the element holding portion 34 of the Karman eddy current detector 33 is transmitted through the wire 37b to the one-dot chain line in FIG. 4 . The temperature sensor circuit and CPU of the circuit section. Furthermore, based on the flow rate value calculated in the arithmetic circuit provided in the CPU based on the eddy current frequency converted from the electrical signal of the piezoelectric element 35, the eddy current frequency due to the temperature is obtained for the fluid provided by the CPU based on the temperature The correction data contained in the correction table of the amount of change is output after temperature correction (pulse and current).

In Table 1 below, when the fluid is water, the maximum flow rate of the flow measuring device is 3 liters/min (liter/min) as 100%, and it is shown that the flow rate is 10 to 100 In the case of %, the eddy current frequency (1/sec) when the temperature of the water is changed to 5°C, 15°C, 25°C, 35°C, 45°C, and 55°C.

[Table 1] flow fluid temperature (L/min) (%FS) 5℃ 15℃ 25℃ 35℃ 45℃ 55℃ 0.3 10 252.5 230.6 215.1 207.1 199.2 192.3 0.6 20 322.3 299.8 284.4 276.4 268.8 262.3 0.9 30 392.0 369.0 353.7 345.7 338.4 332.2 1.2 40 461.8 438.3 423.0 415.0 408 402.2 1.5 50 531.6 507.5 492.4 484.3 477.6 472.2 1.8 60 601.3 576.7 561.7 553.5 547.3 542.1 2.1 70 671.1 646.0 631.0 622.8 616.9 612.1 2.4 80 740.8 715.2 700.4 692.1 686.5 682.1 2.7 90 810.6 784.4 769.7 761.4 756.1 752.0 3.0 100 880.4 853.7 839 830.7 825.7 822.0

As shown in Table 1, when the flow rate is 100% and the temperature is 25°C, the eddy current frequency of 839.0 changes to 880.4 at 5°C. Even if the actual flow rate of the flow is constant, as described above, the eddy current frequency varies depending on the temperature of the fluid, so there is a difference in the output flow rate calculated based on the eddy current frequency. In addition, the frequency of the eddy current due to the Karman vortex largely depends on the shape of the vortex generator and the shape of the flow path. By stabilizing the shape of the eddy current generator and the flow path by molding, the rate of change of the eddy current frequency due to the individual product of each flow measuring device can be made regular. Therefore, the correction of the flow rate can be realized by memorizing the representative value in all the products of the flow measuring device without taking the data of the eddy current frequency due to the change of the fluid temperature for each product of each flow measuring device. Since the viscosity varies with the type of fluid, by obtaining the change data in Table 1 above for various fluids other than water in advance, the fluid can be corrected based on the temperature information of the fluid from the temperature sensor. flow.

Based on the average value of the temperature change table of the eddy current frequency shown in Table 1 obtained by the experiments of individual products of a plurality of flow rate measuring devices, a method was produced so that the eddy current frequency at 1.0000 was set to 1.0000 at a flow rate of 100% and 25°C The normalized table 2 is used as a basic table to be stored in the memory device of the CPU shown in FIG. 4 .

[Table 2] flow fluid temperature (L/min) (%FS) 5℃ 15℃ 25℃ 35℃ 45℃ 55℃ 0.3 10 0.3010 0.2749 0.2564 0.2468 0.2374 0.2292 0.6 20 0.3841 0.3573 0.3390 0.3294 0.3204 0.3126 0.9 30 0.4672 0.4398 0.4216 0.4120 0.4033 0.3959 1.2 40 0.5504 0.5224 0.5042 0.4946 0.4863 0.4794 1.5 50 0.6336 0.6049 0.5869 0.5772 0.5692 0.5628 1.8 60 0.7167 0.6874 0.6695 0.6597 0.6523 0.6461 2.1 70 0.7999 0.770 0.7521 0.7423 0.7353 0.7296 2.4 80 0.8830 0.8524 0.8348 0.8249 0.8182 0.8130 2.7 90 0.9662 0.9349 0.9174 0.9075 0.9012 0.8963 3.0 100 1.0493 1.0175 1.0000 0.9901 0.9841 0.9797

Among the individual products of each flow measuring device, only the vortex frequency at 100% flow rate and 25°C was measured, and the value was multiplied by Table 2. For example, if it is assumed that there is an individual product with a flow rate of 100% and a vortex frequency of 850 (1/sec) at 25°C, then Table 3 is created by multiplying the 850 by the values in Table 2. The table 3 is a correction table for the individual product, and the arithmetic circuit of the CPU shown in FIG. 4 has a correction table.

[table 3] flow fluid temperature (L/min) (%FS) 5℃ 15℃ 25℃ 35℃ 45℃ 55℃ 0.3 10 255.8 233.6 217.9 209.8 201.8 194.8 0.6 20 326.5 303.7 288.1 280.0 272.8 265.7 0.9 30 397.1 373.8 358.3 350.2 342.8 336.6 1.2 40 467.9 444.0 428.5 420.4 413.3 407.5 1.5 50 538.6 514.2 498.9 490.6 483.9 478.4 1.8 60 609.2 584.3 569.1 560.8 554.5 549.2 2.1 70 679.9 654.5 639.3 631.0 625.0 620.1 2.4 80 750.5 724.6 709.6 701.2 695.5 691.0 2.7 90 821.2 794.7 779.8 771.4 766.0 761.9 3.0 100 891.9 864.9 850.0 841.6 836.5 832.8

The specific procedure for correcting the flow rate of the fluid is based on the temperature of the fluid measured by the temperature sensor 36 and the eddy current frequency converted from the electrical signal detected by the piezoelectric element 35 when the flow rate of the fluid is measured , described below.

(1) When the temperature of the fluid measured by the temperature sensor 36 is 15°C, and the eddy current frequency converted from the electrical signal detected by the piezoelectric element 35 is 724.6 (1/sec), in Table 3 There are values in , which are consistent with the temperature and eddy current frequency. Therefore, based on Table 3, when the temperature is 15° C. and the eddy current frequency is 724.6 (1/sec), the CPU shown in FIG. 4 outputs 2.4 (liters/min) as the corrected flow rate.

(2) When the temperature of the fluid measured by the temperature sensor 36 is 25°C, and the eddy current frequency converted from the electrical signal detected by the piezoelectric element 35 is 440 (1/sec), in Table 3 There is no situation in which the temperature is 25°C and the eddy current frequency is 440 (1/sec). According to Table 3, the flow rate in the case where the temperature is 25°C and the vortex frequency 428.5 (1/sec) is 1.2 (L/min), and the flow rate in the case where the temperature is 25°C and the vortex frequency 498.9 (1/sec) is 1.5 (L/min). /min), observing the specific values in Table 3, it can be estimated that there is a linear relationship between the variation of the eddy current frequency and the variation of the flow rate. Therefore, when the temperature is 25° C. and the eddy current frequency is 440 (1/sec), the flow rate after correction can be obtained as follows. 1.2(L/min)+(1.5-1.2)×(440-428.5)/(498.9-428.5)=1.249(L/min) The calculation is performed by the arithmetic circuit of the CPU shown in Figure 4. When the temperature is 25°C and the eddy current frequency is 440 (1/sec), the CPU shown in Figure 4 outputs 1.249 (liters/min) as Corrected flow.

(3) When the temperature of the fluid measured by the temperature sensor 36 is 12°C, and the eddy current frequency converted from the electrical signal detected by the piezoelectric element 35 is 600 (1/sec), in Table 3 There is no situation in which the temperature is 12°C and the eddy current frequency is 600 (1/sec). According to Table 3, the vortex frequency is 255.8 (1/sec) when the temperature is 5°C and the flow rate is 0.3 (L/min), and the vortex frequency is 233.6 (1/sec) when the temperature is 15°C and the flow rate is 0.3 (L/min). /sec), observing the specific values in Table 3, it can be inferred that there is a linear relationship between the change in temperature and the change in eddy current frequency. For this reason, when the temperature is 12° C. and the flow rate is 0.3 (liter/min), the vortex frequency (1/sec) can be obtained as follows. 233.6+(255.8-233.6)×(15-12)/(15-5)=240.3 Similarly, the eddy current frequency (1/sec) can be obtained when the temperature is 12°C and the flow rate is 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.0 (liters/min). The calculation is performed by the arithmetic circuit of the CPU shown in FIG. 4 and stored in the memory device in the CPU.

Table 4 below shows the eddy current frequency (1/sec) when the temperature of the memory device stored in the CPU is 0.3 to 3.0 (liter/min) at 12°C.

[Table 4] flow fluid temperature (L/min) (%FS) 12℃ 0.3 10 240.3 0.6 20 310.6 0.9 30 380.8 1.2 40 451.2 1.5 50 521.5 1.8 60 591.7 2.1 70 662.1 2.4 80 732.4 2.7 90 802.6 3.0 100 873.0

Furthermore, according to Table 4, the flow rate in the case where the temperature is 12°C and the eddy current frequency of 591.7 (1/sec) is 1.8 (liter/min), and the flow rate in the case where the temperature is 12°C and the eddy current frequency of 662.1 (1/sec) is 2.1 (L/min), by observing the specific values in Table 3, it can be inferred that there is a linear relationship between the variation of the eddy current frequency and the variation of the flow rate. Therefore, when the temperature is 12° C. and the eddy current frequency is 600 (1/sec), the flow rate after correction can be obtained as follows. 1.8(L/min)+(2.1-1.8)×(600-591.7)/(662.1-591.7)=1.835(L/min) The arithmetic circuit of the CPU shown in FIG. 4 performs the calculation. When the temperature is 12°C and the eddy current frequency is 600 (1/sec), the CPU shown in FIG. 4 outputs 1.835 (liter/min) as Corrected flow.

[table 5] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 5 0.3 10 0.416 3.88 0.305 0.17 0.6 20 0.725 4.16 0.608 0.25 0.9 30 0.991 3.02 0.903 0.11 1.2 40 1.303 3.43 1.203 0.11 1.5 50 1.627 4.23 1.501 0.04 1.8 60 1.927 4.22 1.796 -0.12 2.1 70 2.222 4.05 2.095 -0.15 2.4 80 2.494 3.13 2.398 -0.06 2.7 90 2.814 3.81 2.698 -0.07 3.0 100 3.121 4.02 3.001 0.03

[Table 6] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 15 0.3 10 0.354 1.81 0.304 0.13 0.6 20 0.651 1.71 0.601 0.02 0.9 30 0.995 1.82 0.913 0.43 1.2 40 1.262 2.08 1.211 0.35 1.5 50 1.569 2.30 1.507 0.24 1.8 60 1.872 2.40 1.802 0.06 2.1 70 2.161 2.04 2.106 0.21 2.4 80 2.466 2.21 2.407 0.22 2.7 90 2.765 2.17 2.705 0.18 3.0 100 3.043 1.44 3.009 0.30

[Table 7] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 25 0.3 10 0.303 0.09 0.308 0.28 0.6 20 0.606 0.20 0.605 0.15 0.9 30 0.903 0.10 0.905 0.17 1.2 40 1.198 -0.06 1.206 0.18 1.5 50 1.505 0.18 1.506 0.20 1.8 60 1.805 0.17 1.808 0.26 2.1 70 2.111 0.38 2.114 0.48 2.4 80 2.409 0.31 2.410 0.33 2.7 90 2.706 0.19 2.706 0.21 3.0 100 3.006 0.20 3.006 0.19

[Table 8] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 35 0.3 10 0.280 -0.65 0.306 0.20 0.6 20 0.577 -0.78 0.612 0.41 0.9 30 0.859 -1.38 0.904 0.14 1.2 40 1.163 -1.24 1.205 0.15 1.5 50 1.480 -0.67 1.508 0.26 1.8 60 1.787 -0.43 1.805 0.18 2.1 70 2.079 -0.72 2.1 10 0.35 2.4 80 2.379 -0.69 2.407 0.23 2.7 90 2.675 -0.82 2.708 0.28 3.0 100 2.977 -0.77 3.006 0.19

[Table 9] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 45 0.3 10 0.262 -1.27 0.307 0.22 0.6 20 0.550 -1.67 0.616 0.55 0.9 30 0.830 -2.33 0.905 0.18 1.2 40 1.135 -2.15 1.207 0.22 1.5 50 1.456 -1.47 1.507 0.25 1.8 60 1.767 -1.09 1.810 0.34 2.1 70 2.062 -1.25 2.104 0.12 2.4 80 2.356 -1.48 2.407 0.22 2.7 90 2.647 -1.76 2.707 0.24 3.0 100 2.951 -1.63 3.006 0.20

[Table 10] Fluid temperature (℃) Base flow Flow meter output (L/min) (%FS) No temperature correction With temperature correction Flow (L/min) Accuracy (%/FS) Flow (L/min) Accuracy (%/FS) 55 0.3 10 0.237 -2.10 0.304 0.13 0.6 20 0.524 -2.53 0.606 0.20 0.9 30 0.814 -2.87 0.912 0.40 1.2 40 1.122 -2.60 1.212 0.40 1.5 50 1.455 -1.50 1.512 0.40 1.8 60 1.752 -1.60 1.804 0.13 2.1 70 2.063 -1.23 2.105 0.17 2.4 80 2.354 -1.53 2.408 0.27 2.7 90 2.648 -1.73 2.707 0.23 3.0 100 2.920 -2.66 3.005 0.17

Tables 5 to 10 use a reference device to fix the temperature and flow rate of the fluid (water), and the accuracy of the output flow rate of the flow measuring device at this time with temperature correction and without temperature correction. comparator. As shown in Tables 5 to 10, the numerical value indicating the accuracy of the case where the temperature correction has been performed is extremely small compared to the case where the temperature correction is not performed. FIG. 5 is a graph showing the accuracy of the case where the temperature correction is not performed by the dotted line (the value is the temperature of the fluid), and the accuracy of the case where the temperature correction has been performed by the solid line. As can be seen in detail from FIG. 5 , the accuracy is improved by performing temperature correction, and the flow rate measuring device of the present invention can accurately measure the flow rate of the fluid regardless of the actual temperature of the fluid.

In Tables 5 to 10, the precisions are the values described below. For example, in Table 10, when the reference flow rate is 0.3 (liter/min), the output flow rate without temperature correction is 0.237 (liter/min), and the difference from the reference flow rate is "-0.063 (liter/min)", Therefore, the ratio (-0.063/3.0) to the full scale (FS) which is 3.0 (liters/minute) is "-2.10%". The "-2.10%" is the accuracy shown in Table 10. In addition, in Table 10, when the reference flow rate is 0.3 (liter/min), the output flow rate with temperature correction is 0.304 (liter/min), and the difference from the reference flow rate is "0.004 (liter/min)", and The ratio (0.004/3.0) to the full scale (FS) which is 3.0 (liters/minute) is "0.13%". The "0.13%" is the accuracy shown in Table 10.

However, there are various types of fluids used by the user, and there are cases where the user uses a fluid different from the fluid targeted for the correction table pre-assembled into the flow measurement device. For this reason, as another embodiment, it is preferable that the flow rate measuring device includes a mechanism that allows the user to correct the flow rate. That is, it is preferable that the flow measurement device has the function that, among the users who purchased the flow measurement device, the user can measure the actual temperature of the fluid measured at a temperature different from the reference temperature. The relationship between the flow rate Q2 of the outgoing fluid and the flow rate Q1 of the fluid measured at the reference temperature corrects the flow rate of the fluid at the actual measured temperature. [Industrial Availability]

As described above, the flow measurement device of the present invention is useful in various fields requiring flow measurement as a flow measurement device capable of reliably correcting measurement errors due to the temperature of the fluid to be measured.

1: flow 2: Karman Eddy Current 3, 13, 32: Eddy current generator 4: Detection element 11: Temperature sensor integrated vortex flowmeter 12, 30: Assay tube 14: Temperature sensor 15: Eddy current detection sensor 16: Measurement room 17: Pressure guide hole 18: Vibration Tube 19: Eddy Current Testing Department 20: Movable tube 21: Pressure plate 22, 31: Flow path 33: Karman Eddy Current Detector 34: Component holding part 35: Piezoelectric elements 36: Temperature sensor 37a, 37b: Wires

Fig. 1 is a schematic structural diagram of the main components of a general vortex flowmeter. FIG. 2 is a schematic cross-sectional view of a conventional vortex flowmeter. Fig. 3 is a schematic structural diagram of an embodiment embodying the flow rate measuring device of the present invention. 4 is a schematic block diagram of a circuit including a CPU having an arithmetic circuit included in the flow measurement device of the present invention. 5 is a graph comparing the accuracy of the flow rate measured by the flow rate measuring device of the present invention with temperature correction and the accuracy without temperature correction.

30: Assay tube

31: flow path

32: Eddy current generator

33: Karman Eddy Current Detector

34: Component holding part

35: Piezoelectric elements

36: Temperature sensor

37a, 37b: Wire

Claims (3)

A flow measurement device comprising: a vortex generator inserted into the flow of a fluid; a detection element for detecting a change in the Karman eddy current generated on the downstream side of the vortex generator as a change in an electrical signal; and a circuit for detecting The electrical signal is converted into an eddy current frequency; and an arithmetic circuit calculates the flow rate of the fluid based on the eddy current frequency; the flow measuring device is characterized in that a temperature sensor is arranged after the detection element, and a temperature sensor is provided in the arithmetic circuit to indicate a preset A correction table of the relationship between the temperature t ₀ , t ₁ , t ₂ , ..., t _n (t ₀ < _{t 1} <t ₂ <... If the temperature of the fluid measured by the above-mentioned temperature sensor is set as t, and the eddy current frequency obtained by converting the electrical signal detected by the above-mentioned detection element is set as f, when the above-mentioned temperature t and the eddy current frequency f and the above-mentioned correction When the temperature of the table matches the eddy current frequency, the flow rate at the matched eddy current frequency is output as the corrected flow rate; when the above-mentioned temperature t corresponds to the temperatures t ₀ , t ₁ , t ₂ ,・・・, or any of t _n , but when the above correction table does not have the above eddy current frequency f, there is a linear relationship between the amount of change in the estimated eddy current frequency and the amount of change in the flow rate, and the eddy current frequency f calculated by the above calculation circuit will be calculated. The flow rate below is output as the corrected flow rate; when the above temperature t does not conform to any of the temperatures in the above correction table, and the temperature t is included in the temperature t ₀ , t ₁ , t ₂ , ..., or t In the case of any two adjacent temperatures t _α and t _β between _n , there is a linear relationship between the estimated temperature change and the eddy current frequency change, and the eddy current frequency at the temperature t is calculated by the above arithmetic circuit, Furthermore, there is a linear relationship between the amount of change in the estimated eddy current frequency and the amount of change in the flow rate Q, and the flow rate at the eddy current frequency f calculated by the arithmetic circuit is output as the corrected flow rate. The flow measurement device of claim 1, wherein the temperature sensor is protected by a chemically resistant material. A flow measuring device, which inserts an obstacle in the flow of the fluid, generates a Karman vortex on the downstream side, detects the change of the eddy current as a change in an electrical signal, and measures the flow of the fluid, the characteristics of the flow measuring device It is to correct the flow rate of the fluid measured at the temperature based on the temperature of the fluid and the relationship between the flow rate Q2 of the fluid measured at a temperature different from the reference temperature and the flow rate Q1 of the fluid measured at the reference temperature.

Images